Class generate key RSA

RSAKeyGen.java

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package onthi;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.PrivateKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import javax.crypto.KeyGenerator;

/**
 *
 * @author SeVenT
 */
public class SinhKhoaRSA {

    private KeyPairGenerator keygen;
    private KeyPair keypair;
    private PublicKey pubkey;
    private PrivateKey prikey;

    public SinhKhoaRSA(int dodai) throws Exception {
        keygen = KeyPairGenerator.getInstance("RSA");
        keygen.initialize(dodai);

        keypair = keygen.generateKeyPair();
        pubkey = keypair.getPublic();
        prikey = keypair.getPrivate();
    }

    public void ghifile(String duong_dan, byte[] du_lieu) throws Exception {
        File f = new File(duong_dan);
        f.getParentFile().mkdir();
        FileOutputStream fo = new FileOutputStream(f);
        fo.write(du_lieu);
        fo.flush();
        fo.close();
    }

    public byte[] docfile(String duong_dan) throws IOException {
        byte[] bytes;
        File file = new File(duong_dan);
        bytes = Files.readAllBytes(file.toPath());
        return bytes;
    }

    public PublicKey sinhKhoaCongKhai(byte[] du_lieu) throws Exception{
        PublicKey khoa_cong_khai;
        X509EncodedKeySpec spec = new X509EncodedKeySpec(du_lieu);
        KeyFactory bo_sinh_khoa = KeyFactory.getInstance("RSA");
        khoa_cong_khai = bo_sinh_khoa.generatePublic(spec);
        return khoa_cong_khai;
    }

    public PrivateKey sinhKhoaBiMat(byte[] du_lieu) throws Exception{
        PrivateKey khoa_bi_mat;
        PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(du_lieu);
        KeyFactory bo_sinh_khoa = KeyFactory.getInstance("RSA");
        khoa_bi_mat = bo_sinh_khoa.generatePrivate(spec);
        return khoa_bi_mat;
    }
    
     public PublicKey getPub() {
        return pubkey;
    }

    public PrivateKey getPri() {
        return prikey;
    }
}